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Discussion Starter · #1 ·
Quick brief... '16 FoST FBO tuning e30. I was having a persistent p0088. I replaced the sensor on the fuel line near the firewall and nothing. Picked up a super cheap HPFP and it threw a p0088, cleared it, and then it threw a p0087. I'm thinking the HPFP I picked up might be bad??? I'm confused lol please help.
 

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We need a lot more information about your setup in order to help.
 

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Discussion Starter · #3 ·
Green Filter, Boomba BoV routed to true vacuum, boomba RMM, JBR shift arm, short shifter and base, cable, bracket bushings. Straight piped, stock DP. ESP fmic.
 

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Well P0088 is saying that your HP fuel system is too high.
The P0087 is low pressure fuel delivery.

E30 requires more fuel volume to reach its power goals, especially on the low end of things.

Have you discussed any of this with your tuner? Do you have logs to post?
 

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Well P0088 is saying that your HP fuel system is too high.
The P0087 is low pressure fuel delivery.

E30 requires more fuel volume to reach its power goals, especially on the low end of things.

Have you discussed any of this with your tuner? Do you have logs to post?
Perhaps Ethanol to Gas ratio is off, e.g. he has too much E.
 

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Discussion Starter · #7 ·
Not tuned by JST, my tuner and I have discussed it at lengths. With my original HPFP I would run rich and have backfires. We decided on changing the sensor on the fuel line itself near the firewall, and it still threw a p0088. I came across a $30 pump of a parts car and it threw a p0087. I'm going to put back on my original since I'd rather run rich than lean. The image is from a p0088 log
Screenshot_20210514-134916_Gmail.jpg
 

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Discussion Starter · #8 ·
Perhaps Ethanol to Gas ratio is off, e.g. he has too much E.
I could have had a dyslexic moment the last fill up, but it did it on my 93 tune as well(the p0088) we tried e30 tune to see if it would react differently and it didn't.
 

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Not sure. It could be a bad HPFP, bad sensor...

One common thing I've seen a lot is some tuners crank up the voltage on the HPFP to max out the fuel rail pressure. It causes some of these codes, and goes away once the tuner revises it.
 

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The low pressure pump sensor is located at the firewall and the high pressure fuel pump sensor is at the rail on the passenger side.

Both the low and high pressure system work in concert with one another.

The electrical in tank low pressure pump supply is responsible for volume, while the higher pressure mechanical pressure delivers fuel directly into the cylinder.

The direct injector only has a 10 ms window to operate vs it's port injection counterpart at 20 ms. If you are taxing the factory fuel system it may be time to look into aux fueling.
 
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Discussion Starter · #11 ·
Not sure. It could be a bad HPFP, bad sensor...

One common thing I've seen a lot is some tuners crank up the voltage on the HPFP to max out the fuel rail pressure. It causes some of these codes, and goes away once the tuner revises it.
My tuner said he hasn't/doesn't touch voltage from stock.
 

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Do you any logs showing both low and rail pressure?
 

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So low desired is 94.4 and actual is 108.8?
14 PSI discrepancy is enough to trigger a DTC. When was the last time you reset your KAM?
 

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Discussion Starter · #15 ·
Not sure honestly, I know I have but not recently. I know I reset the ecu learning the other day. My mechanic is lost as well. He reached out to my tuner and they spoke. My tuner doesn't touch any fuel trims, so the only thoughts my mechanic had was a possible clog somewhere and to try seafoam in the fuel tank and if that doesn't work then a new tuner...
 
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